Positive allosteric modulation of the ionotropic glutamate receptor GluA2 presents a potential treatment of cognitive disorders, for example, Alzheimer’s disease. In the present study, we describe the ... [more ▼]

Positive allosteric modulation of the ionotropic glutamate receptor GluA2 presents a potential treatment of cognitive disorders, for example, Alzheimer’s disease. In the present study, we describe the synthesis, pharmacology, and thermodynamic studies of a series of monofluoro-substituted 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides. Measurements of ligand binding by isothermal titration calorimetry (ITC) showed similar binding affinities for the modulator series at the GluA2 LBD but differences in the thermodynamic driving forces. Binding of 5c (7-F) and 6 (no-F) is enthalpy driven, and 5a (5-F) and 5b (6-F) are entropy driven. For 5d (8-F), both quantities were equal in size. Thermodynamic integration (TI) and one-step perturbation (OSP) were used to calculate the relative binding affinity of the modulators. The OSP calculations had a higher predictive power than those from TI, and combined with the shorter total simulation time, we found the OSP method to be more effective for this setup. Furthermore, from the molecular dynamics simulations, we extracted the enthalpies and entropies, and along with the ITC data, this suggested that the differences in binding free energies are largely explained by the direct ligand-surrounding enthalpies. Furthermore, we used the OSP setup to predict binding affinities for a series of polysubstituted fluorine compounds and monosubstituted methyl compounds and used these predictions to characterize the modulator binding pocket for this scaffold of positive allosteric modulators.10.1021/ci500559b [less ▲]

Two 4-ethyl-substituted pyridothiadiazine dioxides belonging to α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor positive allosteric modulators were cocrystallized with the GluA2 ligand binding domain in order to decipher the impact of the position of the nitrogen atom on their binding mode at the AMPA receptors. The latter was found to be very similar to that of previously described benzothiadiazine-type AMPA receptor modulators. The affinity of the two compounds for the receptor was determined by isothermal titration calorimetry. Accordingly, the synthesis and biological evaluation of novel 4-cyclopropyl-substituted pyridothiadiazine dioxides was performed and completed with the synthesis of the corresponding chloro-substituted 4-cyclopropyl-3,4-dihydro-2H-benzothiadiazine 1,1-dioxides. The “8-aza” compound 32 was found to be the most potent pyridothiadiazine-type AMPA receptor potentiator in vitro, whereas the 7-chloro-substituted compound 36c emerged as the most promising benzothiadiazine dioxide. Due to proper drug-likeness and low in vivo acute toxicity in mice, 36c was chosen for a more complete preclinical evaluation. The compound was able to easily cross the blood–brain barrier. In an in vivo object recognition test with CD1 mice, oral administration of 36c was found to significantly improve cognition performance at doses as low as 1 mg/kg. [less ▲]

Positive allosteric modulators of ionotropic glutamate receptors are potential compounds for treatment of cognitive disorders, e.g., Alzheimer’s disease. The modulators bind within the dimer interface of the ligand-binding domain (LBD) and stabilize the agonist-bound conformation, thereby slowing receptor desensitization and/or deactivation. Here we describe the synthesis and pharmacological testing at GluA2 of a new generation of 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides. The most potent modulator 3 in complex with GluA2-LBD-L483Y-N754S was subjected to structural analysis by X-ray crystallography, and the thermodynamics of binding was studied by isothermal titration calorimetry. Compound 3 binds to GluA2-LBD-L483Y-N754S with a Kd of 0.35 μM (ΔH = −7.5 kcal/mol and −TΔS = −1.3 kcal/mol). This is the first time that submicromolar binding affinity has been achieved for this type of positive allosteric modulator. The major structural factor increasing the binding affinity of 3 seems to be interactions between the cyclopropyl group of 3 and the backbone of Phe495 and Met496. [less ▲]

Positive allosteric modulators of ionotropic glutamate receptors are potential compounds for treatment of cognitive disorders, e.g., Alzheimer’s disease. The modulators bind within the dimer interface of the ligand-binding domain (LBD) and stabilize the agonist-bound conformation, thereby slowing receptor desensitization and/or deactivation. Here we describe the synthesis and pharmacological testing at GluA2 of a new generation of 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides. The most potent modulator 3 in complex with GluA2-LBD-L483Y-N754S was subjected to structural analysis by X-ray crystallography, and the thermodynamics of binding was studied by isothermal titration calorimetry. Compound 3 binds to GluA2-LBD-L483Y-N754S with a Kd of 0.35 μM (ΔH = −7.5 kcal/mol and −TΔS = −1.3 kcal/mol). This is the first time that submicromolar binding affinity has been achieved for this type of positive allosteric modulator. The major structural factor increasing the binding affinity of 3 seems to be interactions between the cyclopropyl group of 3 and the backbone of Phe495 and Met496. [less ▲]

On the basis of the results obtained in previous series of AMPA potentiators belonging to 3,4-dihydro-2H-benzo- and 3,4-dihydro-2H-pyrido-1,2,4-thiadiazine 1,1-dioxides, the present work focuses on the ... [more ▼]

On the basis of the results obtained in previous series of AMPA potentiators belonging to 3,4-dihydro-2H-benzo- and 3,4-dihydro-2H-pyrido-1,2,4-thiadiazine 1,1-dioxides, the present work focuses on the design of original isosteric 3,4-dihydro-2H-thieno-1,2,4-thiadiazine 1,1-dioxides. Owing to the sulfur position, three series of compounds were developed and their activity as AMPA potentiators was characterized. In each of the developed series, potent compounds were discovered. After screening the selected active compounds on a safety in vivo test, 6-chloro-4-ethyl-3,4-dihydro-2H-thieno[2,3-e]-1,2,4-thiadiazine 1,1-dioxide (24) appeared as the most promising compound and was further evaluated. Its effects on long-term potentiation in vivo and on AMPA-mediated noradrenaline release were measured to predict its potential cognitive enhancing properties. Finally, an object recognition test performed in mice revealed that 24 was able to significantly enhance cognition, after oral administration, at doses as low as 0.3 mg/kg. This study validates the interest of the isosteric replacement of the benzene or pyridine nuclei by the thiophene nucleus in the ring-fused thiadiazine dioxides class of AMPA potentiators. [less ▲]

AMPA receptor potentiators belonging to 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides have been found to be of great interest as cognitive enhancers. Previous structure–activity relationships have ... [more ▼]

AMPA receptor potentiators belonging to 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides have been found to be of great interest as cognitive enhancers. Previous structure–activity relationships have demonstrated the importance for activity of the nature of the substituent at the 7-position of the heterocycle. This work aims to explore the impact on AMPA potentiation of the introduction of different aryl and aralkyl ester or aryl amide groups at the 7-position. The new synthesized compounds were evaluated as AMPA receptor potentiators by examining their effect on rat brain primary cell cultures on AMPA-evoked membrane depolarisation using fluorescent membrane potential dyes and on imaging-based plate reader. The most potent compound of this series was 2-methylphenyl 4-methyl- 3,4-dihydro-2H-1,2,4-benzothiadiazine-7-carboxylate 1,1-dioxide 16c which provoked a strong potentiation of AMPA current with a potency close to that reported for the best reference compounds of the benzothiadiazine class (i.e cyclothiazide). This work also revealed that only the ortho-substitution of the phenyl group of 1,2,4-benzothiadiazine-7-carboxylate esters provided potent AMPA receptor potentiators opening the way to further chemical exploration. [less ▲]

In the search of a potent cognitive enhancer, a series of 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides have been synthesized and evaluated as positive allosteric modulators of the AMPA receptors. In ... [more ▼]

In the search of a potent cognitive enhancer, a series of 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides have been synthesized and evaluated as positive allosteric modulators of the AMPA receptors. In the present work, we focused our efforts on the insertion of mono- or polyfluoro- substituted alkyl chains at the 4-position of the thiadiazine ring in an attempt to enhance the pharmacokinetic behavior of previously described compounds. Among all the described compounds, 7-chloro-4-(2-fluoroethyl)-3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide, 12b, was shown to exert a strong activity on AMPA receptors in vitro and a marked cognitive-enhancing effect in vivo after oral administration to Wistar rats. Considering its in vivo activity, the metabolic degradation of 12b was studied and compared to that of its nonfluorinated analogue 9b. Taken together, results of this study clearly validated the positive impact of the fluorine atom on the alkyl chain at the 4-position of benzothiadiazine dioxides on activity and metabolic stability. [less ▲]

Taking into account structure-activity relationships obtained with our previous series, new diversely substituted 1,2,4-pyridothiadiazine 1,1-dioxides were designed to obtain novel AMPA potentiators. The aim of this work was focused on the improvement of lipophilicity, which is well known as a critical parameter to obtain in vivo active central nervous system agents. For this purpose, two positions on the pyridine ring were privileged to insert selected groups. Among the synthesized compounds emerged 7-chloro-4-ethyl-3,4-dihydro-2H-pyrido[2,3-e]-[1,2,4]-thiadiazine 1,1-dioxide (12d), which was evaluated in two memory tests in Wistar rats and showed cognition enhancing effects after intraperitoneal injection at doses as low as 0.3mg/kg. [less ▲]

A series of 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides have been synthesized and evaluated as potentiators of AMPA receptors. Attention was paid to the impact of the substituent introduced at the ... [more ▼]

A series of 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides have been synthesized and evaluated as potentiators of AMPA receptors. Attention was paid to the impact of the substituent introduced at the 7-position of the heterocycle. The biological evaluation was achieved by measuring the AMPA current in rat cortex mRNA-injected Xenopus oocytes. The most potent compound, 4-ethyl-7-fluoro-3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide (12a) was found to be active in an object recognition test in rats demonstrating cognition enhancing effects in vivo after oral administration. [less ▲]